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diff --git a/www/c3ref/preupdate_blobwrite.html b/www/c3ref/preupdate_blobwrite.html new file mode 100644 index 0000000..454f521 --- /dev/null +++ b/www/c3ref/preupdate_blobwrite.html @@ -0,0 +1,241 @@ +<!DOCTYPE html> +<html><head> +<meta name="viewport" content="width=device-width, initial-scale=1.0"> +<meta http-equiv="content-type" content="text/html; charset=UTF-8"> +<link href="../sqlite.css" rel="stylesheet"> +<title>The pre-update hook.</title> +<!-- path=../ --> +</head> +<body> +<div class=nosearch> +<a href="../index.html"> +<img class="logo" src="../images/sqlite370_banner.gif" alt="SQLite" border="0"> +</a> +<div><!-- IE hack to prevent disappearing logo --></div> +<div class="tagline desktoponly"> +Small. Fast. 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+if( w.style.display=="block" ){ +w.style.display = "none"; +}else{ +w.style.display = "block"; +} +} +function toggle_search() { +var w = document.getElementById("searchmenu"); +if( w.style.display=="block" ){ +w.style.display = "none"; +} else { +w.style.display = "block"; +setTimeout(function(){ +document.getElementById("searchbox").focus() +}, 30); +} +} +function div_off(nm){document.getElementById(nm).style.display="none";} +window.onbeforeunload = function(e){div_off("submenu");} +/* Disable the Search feature if we are not operating from CGI, since */ +/* Search is accomplished using CGI and will not work without it. */ +if( !location.origin || !location.origin.match || !location.origin.match(/http/) ){ +document.getElementById("search_menubutton").style.display = "none"; +} +/* Used by the Hide/Show button beside syntax diagrams, to toggle the */ +function hideorshow(btn,obj){ +var x = document.getElementById(obj); +var b = document.getElementById(btn); +if( x.style.display!='none' ){ +x.style.display = 'none'; +b.innerHTML='show'; +}else{ +x.style.display = ''; +b.innerHTML='hide'; +} +return false; +} +var antiRobot = 0; +function antiRobotGo(){ +if( antiRobot!=3 ) return; +antiRobot = 7; +var j = document.getElementById("mtimelink"); +if(j && j.hasAttribute("data-href")) j.href=j.getAttribute("data-href"); +} +function antiRobotDefense(){ +document.body.onmousedown=function(){ +antiRobot |= 2; +antiRobotGo(); +document.body.onmousedown=null; +} +document.body.onmousemove=function(){ +antiRobot |= 2; +antiRobotGo(); +document.body.onmousemove=null; +} +setTimeout(function(){ +antiRobot |= 1; +antiRobotGo(); +}, 100) +antiRobotGo(); +} +antiRobotDefense(); +</script> +<!-- keywords: sqlite3_preupdate_blobwrite sqlite3_preupdate_count sqlite3_preupdate_depth sqlite3_preupdate_hook sqlite3_preupdate_new sqlite3_preupdate_old --> +<div class=nosearch> +<a href="../c3ref/intro.html"><h2>SQLite C Interface</h2></a> +<h2>The pre-update hook.</h2> +</div> +<blockquote><pre> +#if defined(SQLITE_ENABLE_PREUPDATE_HOOK) +void *sqlite3_preupdate_hook( + sqlite3 *db, + void(*xPreUpdate)( + void *pCtx, /* Copy of third arg to preupdate_hook() */ + sqlite3 *db, /* Database handle */ + int op, /* SQLITE_UPDATE, DELETE or INSERT */ + char const *zDb, /* Database name */ + char const *zName, /* Table name */ + sqlite3_int64 iKey1, /* Rowid of row about to be deleted/updated */ + sqlite3_int64 iKey2 /* New rowid value (for a rowid UPDATE) */ + ), + void* +); +int sqlite3_preupdate_old(sqlite3 *, int, sqlite3_value **); +int sqlite3_preupdate_count(sqlite3 *); +int sqlite3_preupdate_depth(sqlite3 *); +int sqlite3_preupdate_new(sqlite3 *, int, sqlite3_value **); +int sqlite3_preupdate_blobwrite(sqlite3 *); +#endif +</pre></blockquote> +<p> +These interfaces are only available if SQLite is compiled using the +<a href="../compile.html#enable_preupdate_hook">SQLITE_ENABLE_PREUPDATE_HOOK</a> compile-time option.</p> + +<p>The <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_hook()</a> interface registers a callback function +that is invoked prior to each <a href="../lang_insert.html">INSERT</a>, <a href="../lang_update.html">UPDATE</a>, and <a href="../lang_delete.html">DELETE</a> operation +on a database table. +At most one preupdate hook may be registered at a time on a single +<a href="../c3ref/sqlite3.html">database connection</a>; each call to <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_hook()</a> overrides +the previous setting. +The preupdate hook is disabled by invoking <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_hook()</a> +with a NULL pointer as the second parameter. +The third parameter to <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_hook()</a> is passed through as +the first parameter to callbacks.</p> + +<p>The preupdate hook only fires for changes to real database tables; the +preupdate hook is not invoked for changes to <a href="../vtab.html">virtual tables</a> or to +system tables like sqlite_sequence or sqlite_stat1.</p> + +<p>The second parameter to the preupdate callback is a pointer to +the <a href="../c3ref/sqlite3.html">database connection</a> that registered the preupdate hook. +The third parameter to the preupdate callback is one of the constants +<a href="../c3ref/c_alter_table.html">SQLITE_INSERT</a>, <a href="../c3ref/c_alter_table.html">SQLITE_DELETE</a>, or <a href="../c3ref/c_alter_table.html">SQLITE_UPDATE</a> to identify the +kind of update operation that is about to occur. +The fourth parameter to the preupdate callback is the name of the +database within the database connection that is being modified. This +will be "main" for the main database or "temp" for TEMP tables or +the name given after the AS keyword in the <a href="../lang_attach.html">ATTACH</a> statement for attached +databases. +The fifth parameter to the preupdate callback is the name of the +table that is being modified.</p> + +<p>For an UPDATE or DELETE operation on a <a href="../rowidtable.html">rowid table</a>, the sixth +parameter passed to the preupdate callback is the initial <a href="../lang_createtable.html#rowid">rowid</a> of the +row being modified or deleted. For an INSERT operation on a rowid table, +or any operation on a WITHOUT ROWID table, the value of the sixth +parameter is undefined. For an INSERT or UPDATE on a rowid table the +seventh parameter is the final rowid value of the row being inserted +or updated. The value of the seventh parameter passed to the callback +function is not defined for operations on WITHOUT ROWID tables, or for +DELETE operations on rowid tables.</p> + +<p>The sqlite3_preupdate_hook(D,C,P) function returns the P argument from +the previous call on the same <a href="../c3ref/sqlite3.html">database connection</a> D, or NULL for +the first call on D.</p> + +<p>The <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_old()</a>, <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_new()</a>, +<a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_count()</a>, and <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_depth()</a> interfaces +provide additional information about a preupdate event. These routines +may only be called from within a preupdate callback. Invoking any of +these routines from outside of a preupdate callback or with a +<a href="../c3ref/sqlite3.html">database connection</a> pointer that is different from the one supplied +to the preupdate callback results in undefined and probably undesirable +behavior.</p> + +<p>The <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_count(D)</a> interface returns the number of columns +in the row that is being inserted, updated, or deleted.</p> + +<p>The <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_old(D,N,P)</a> interface writes into P a pointer to +a <a href="../c3ref/value.html">protected sqlite3_value</a> that contains the value of the Nth column of +the table row before it is updated. The N parameter must be between 0 +and one less than the number of columns or the behavior will be +undefined. This must only be used within SQLITE_UPDATE and SQLITE_DELETE +preupdate callbacks; if it is used by an SQLITE_INSERT callback then the +behavior is undefined. The <a href="../c3ref/value.html">sqlite3_value</a> that P points to +will be destroyed when the preupdate callback returns.</p> + +<p>The <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_new(D,N,P)</a> interface writes into P a pointer to +a <a href="../c3ref/value.html">protected sqlite3_value</a> that contains the value of the Nth column of +the table row after it is updated. The N parameter must be between 0 +and one less than the number of columns or the behavior will be +undefined. This must only be used within SQLITE_INSERT and SQLITE_UPDATE +preupdate callbacks; if it is used by an SQLITE_DELETE callback then the +behavior is undefined. The <a href="../c3ref/value.html">sqlite3_value</a> that P points to +will be destroyed when the preupdate callback returns.</p> + +<p>The <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_depth(D)</a> interface returns 0 if the preupdate +callback was invoked as a result of a direct insert, update, or delete +operation; or 1 for inserts, updates, or deletes invoked by top-level +triggers; or 2 for changes resulting from triggers called by top-level +triggers; and so forth.</p> + +<p>When the <a href="../c3ref/blob_write.html">sqlite3_blob_write()</a> API is used to update a blob column, +the pre-update hook is invoked with SQLITE_DELETE. This is because the +in this case the new values are not available. In this case, when a +callback made with op==SQLITE_DELETE is actually a write using the +sqlite3_blob_write() API, the <a href="../c3ref/preupdate_blobwrite.html">sqlite3_preupdate_blobwrite()</a> returns +the index of the column being written. In other cases, where the +pre-update hook is being invoked for some other reason, including a +regular DELETE, sqlite3_preupdate_blobwrite() returns -1.</p> + +<p>See also: <a href="../c3ref/update_hook.html">sqlite3_update_hook()</a> +</p><p>See also lists of + <a href="../c3ref/objlist.html">Objects</a>, + <a href="../c3ref/constlist.html">Constants</a>, and + <a href="../c3ref/funclist.html">Functions</a>.</p> + |